It is a good thing that you wish to unburden your soul by confessing sins.
Why wouldn't you speak to the priest regardless of your intentions about entering the Church? Did someone tell you not to talk to the priest? Why not call up the Church and make an appointment to talk to him? You could tell him that you are scared and embarassed. I'm sure he's heard the same thing many times.
Sometimes I feel afraid of my priest, whom I trust with the welfare of my soul. I think this is just another temptation to ignore.
What i am afraid of is this: that i tell him about the thing (mortal sin) and make a so bad first impression that the doors closes on me before they really have been opened, if you see what i mean? Writing this makes me feel like Doink the clown. But it is from my heart. Last sunday at divine liturgy, i realized what a nice little family this is. Thinking to myself that one day it would be so awesome to be a part of it.
But, one step at a time. In the meantime, all i can do and have done, is to pray (psalms 37,38, 50,51,62,63,103, 140, 141, 142, 143 to mention some from my dayily prayerrule and offer it up to God). It would have been so nice to seek advice, but im afraid to appear like a complete joke.